Microwave Spectrum of Tertiary Butyl Chloride. A Comparison of Tertiary Butyl Structures

The rotational constants of (C12H3)3C12Cl35, (C12H3)3C12Cl37, (C12H3)3C13Cl35, (C12H3)3C13Cl37, and (C13H3) (C12H3)2C12Cl35 have been measured. The rs structure of the t-butyl chloride skeleton calculated from these constants is: r(CCl) = 1.803±0.002 Å, r(CC) = 1.530±0.002 Å,∠CCC=110.9°±0.1°. The quadrupole coupling constant for Cl35 is −66.9±1.5 Mc. The structures of a number of t-butyl compounds are compared. The t-butyl group is practically unaffected by substitution, while the CX bond in (CH3)3CX is systematically longer than in CH3X molecules. Conventional concepts of valence theory do not provide a satisfying explanation for this behavior.